We propose to study the prevalence of and outcomes associated with human immunodeficiency virus (HIV) infection in pregnant women and their delivered infants in Rwanda. Our studies will determine the point and period prevalences of HIV antibody in pregnant women; determine the probability of infants infection with HIV at age 9 months, given maternal positivity at birth; determine the probability of infant mortality or severe morbidity over two years, given maternal infection at birth; determine the probability of and risk factors for seroconversion to HIV over two years, given seronegativity in mother and infant at birth; and determine the probability of adverse maternal outcome over two years, given seropositivity at study entry. The general study design is that of a concurrent prospective study. The study populations will be drawn from women making their first prenatal visit to one of three clinics in Rwanda. The first 100 woman attending each clinic each quarter will be tested for antibody to HIV This surveillance will continue for 4 years. In one site cohorts of 150 seropositive and 300 seronegative pregnant women will be established and followed prospectively until their delivered infants are two years of age. These mothers and infants will be examined at infant ages 1-3, 6, 9, 12, 18, and 24 months. Responses to interview questionnaires, presence of antibody to HIV, and records of growth will provide the data for assessing primary outcomes. Vital status will be ascertained for participants failing to appear for follow-up. Interview data will be entered locally on floppy disk via optical scanner and microcomputer, and verified and analyzed centrally. Serologic testing will be performed both locally and at the study center at Johns Hopkins University, utilizing sera collected on filter papers. Data analysis will include use of stratified analyses, logistic regression models, life table methods, and autoregressive models appropriate to longitudinal data.